To clean a closed enclosure, it is known practice to make two openings in the enclosure in order to cause a fluid, gaseous or liquid, where necessary having chemical cleaning properties, to circulate therein at high pressure. This method rapidly reaches its limits:                for certain complex shapes of the enclosure, walls remain unreachable by the fluid and uncleaned;        in addition, simple circulation requires a relatively long cleaning time and generally represents mediocre effectiveness.        
To fill an air-filled closed or semi-closed cavity with a liquid or pasty substance, it is known practice to connect a water inlet duct in an opening of the cavity and to provide a discharge of the air, either through a second opening or through the same opening. Such a method is however lengthy if the volume is great. In addition, it does not make it possible to perfectly fill a cavity whose shape is complex, has thin and narrow ramifications, in which air pockets remain trapped.